Various rapid solidification processes are known for rapidly quenching molten material into useful metals, alloys and non-metals. In rapid solidification through the ordinary melt-spinning technique, the material to be processed is typically heated in a crucible having an orifice, and is ejected through the orifice as a molten jet onto a rapidly spinning disk of high thermal conductivity. The molten jet is rapidly quenched by the rapidly spinning disk and released therefrom typically as a filament.
An arc furnace having a water-cooled copper crucible for the melt-spinning of refractory and reactive metals and alloys is reported by Sung-Hyun Whang et al. in an article entitled, "An Arc Furnace Melt Spinner for the RSR Processing of Refractory and Reactive Alloys," appearing in Rapid Solidification Processing, Principles and Technologies, III, National Bureau of Standards, Maryland (December 1982), incorporated herein by reference. The reported arc furnace melt spinner includes a water-cooled copper crucible having a central orifice that is positioned between upper and lower processing chambers in such a way that the chambers are only in fluid communication via the orifice of the crucible. An upper chamber electrode melts and superheats a metal or other material to be melt-spun in the cooled crucible, and a spinning disk is provided in the lower chamber and adjacent the orifice. The chambers are equally pressurized during heating, and the lower chamber is rapidly evacuated during melt-spinning creating a suction which draws the superheated melt through the orifice as a molten jet onto the spinning disk upon which it is rapidly quenched and released as a filament.
In order to create novel microstructures and metal and alloy materials, selected refractory and reactive metals and alloys must be quenched not only rapidly but in a continuous way. Among other material impediments to continuous casting, the superheated melt tends to "freeze" on the confronting wall of the cooled crucible therewith constricting and/or occluding totally the orifice of the crucible. The rate of flow and quantity of material of the molten jet thus either varies, providing non-repeatable casting, or ceases altogether. Moreover, between casting, the "frozen" layer of melt must be physically removed from the crucible and orifice. The removal process, however, often deforms the maleable copper crucible and orifice thereof to such an extent as to necessitate its removal and replacement by another crucible. Furthermore, the heat that is lost from the melt to the cooled crucible in use must be continuously replenished by supplying such additional electrical power as to maintain the molten state, thus necessitating a comparatively large power consumption.